New research reveals that flu-positive individuals did not transmit the virus to healthy adults during a controlled study, suggesting key factors that may reduce flu transmission.
This year’s flu season has been characterized by an aggressive new strain, leading to record-high hospitalizations and severe symptoms across the United States. As public health officials seek ways to curb the spread of influenza, a groundbreaking study has uncovered several factors that may significantly reduce transmission rates.
Researchers from the University of Maryland Schools of Public Health and Engineering, alongside the School of Medicine in Baltimore, conducted a unique study on influenza transmission. They placed flu-positive college students in a hotel room with healthy middle-aged adult volunteers to observe potential virus spread.
The study, published in the journal PLOS Pathogens, is reportedly the first clinical trial to investigate how the flu spreads from naturally infected individuals to uninfected ones. A total of 11 healthy volunteers participated in the trial, living on a quarantined floor of a Baltimore-area hotel for two weeks. During this period, they engaged in various simulated interactions, including conversations, physical activities like yoga, and sharing objects such as pens and tablets.
Throughout the study, researchers closely monitored the participants for symptoms, conducted daily nasal swabs, and collected saliva and blood samples to test for antibodies. They also measured the “viral exposure” in the volunteers’ breathing air and the ambient air in the activity room. A specialized machine called the Gesundheit II, developed by Dr. Donald Milton and colleagues at Harvard T.H. Chan School of Public Health, was used to assess the exhaled breath of the participants.
At the conclusion of the experiment, none of the healthy individuals contracted the flu, a finding attributed to several factors. Notably, the infected students exhibited minimal coughing, which researchers noted was crucial since they were retaining “a lot of virus in their noses” and only releasing small amounts into the air.
Dr. Jianyu Lai, the study’s lead data analyst, emphasized that coughing is a significant factor in flu transmission. “Our data suggests key things that increase the likelihood of flu transmission — coughing is a major one,” he stated in a press release.
Another important factor identified was the ventilation and air movement within the study room. The air was continuously mixed by a heater and dehumidifier, which diluted the small amounts of virus present in the air. Lai pointed out that middle-aged adults typically exhibit lower susceptibility to influenza compared to younger adults.
Dr. Donald Milton, a professor at the University of Maryland’s Department of Global, Environmental and Occupational Health and an expert in infectious disease aerobiology, noted that most researchers assume airborne transmission is a primary mode of disease spread. “At this time of year, it seems like everyone is catching the flu virus, and yet our study showed no transmission,” he remarked. “What does this say about how flu spreads and how to stop outbreaks?”
Milton, who was among the first experts to identify effective measures to halt the spread of COVID-19, stressed the importance of findings from such trials in updating international infection-control guidelines. “Being up close, face-to-face with other people indoors where the air isn’t moving much, seems to be the most risky thing — and it’s something we all tend to do a lot,” he explained.
He further suggested that portable air purifiers, which can both stir up and clean the air, could be beneficial in reducing transmission risks. However, he cautioned that if individuals are in close proximity and someone is coughing, wearing a mask, particularly an N95, remains the best preventive measure.
According to data from the Centers for Disease Control and Prevention (CDC), approximately 11 million flu illnesses and around 5,000 deaths have been reported so far in the 2025-2026 influenza season. A significant portion of current flu cases is attributed to the new influenza A subclade K variant.
These findings could reshape our understanding of flu transmission and inform public health strategies aimed at mitigating outbreaks in the future, according to Source Name.